1. Field of the Invention
The present invention relates generally to a device and method for controlling a hybrid vehicle and more specifically to controlling a hybrid vehicle including an internal combustion engine.
2. Description of the Background Art
A hybrid vehicle including an internal combustion engine and an electric motor is generally known. The hybrid vehicle may have the electric motor operated to perform regenerative braking to recover energy. In regenerative braking, when braking force is requested, the electric motor converts the hybrid vehicle's kinetic energy into electrical energy to thus generate braking force and also charge a rechargeable battery.
For example, Japanese Patent Laying-Open No. 2005-137091 discloses a hybrid vehicle capable of regenerative braking. The hybrid vehicle includes a rechargeable battery to store electric power generated through regenerative braking and refers to the rechargeable battery's degradation degree to limit electric power charged in regenerative braking. This allows the rechargeable battery to have an extended lifetime.
Furthermore, a hybrid vehicle may have mounted therein an internal combustion engine having a variable valve actuation device for varying an actuation characteristic of an intake valve of the internal combustion engine. Some variable valve actuation device is configured to vary at least one of an amount of lifting an intake valve and a working angle on the intake valve (see Japanese Patent Laying-Open Nos. 2004-183610, 2013-053610, 2008-025550, 2012-117376, and 09-242519, for example). The variable valve actuation device allows the internal combustion engine to exhibit a modified operational characteristic.
A hybrid vehicle may implement requested engine braking force by braking force of regenerative braking. In that case, ensuring that the requested engine braking force is implemented is important, and accordingly, if regenerative braking generates electric power exceeding that which the rechargeable battery can accept, regenerative braking must be performed, and it may be difficult to prevent the rechargeable battery from degrading.